[Bug tree-optimization/107409] Perf loss ~5% on 519.lbm_r SPEC cpu2017 benchmark with r10-5090-ga9a4edf0e71bba

[rvmallad at amazon dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107409

--- Comment #12 from Rama Malladi <rvmallad at amazon dot com> ---
I found difference in dumps at various stages of the compilation for the
mainline GCC and with update_max_bb_count() commented. Here are the details:

Mainline: Commit ID: 63a42ffc0833553fbcb84b50cf0fd2d867b8a92f

There was difference in the dumps for these 2 stages:
"einline" and "earlydebug"

Since we use LTO for this build of 519.lbm_r build, I found these differences
in these stages of the link-time optimizer:
"vect", "slp1", "ivopts", "earlydebug", "debug"

Also, this perf drop of 5%-6% with update_max_bb_count() code was observed only
on ARM64 instances (Graviton3) and not on x86_64 instances (Intel Xeon).

I ran the other SPEC cpu2017_fprate benchmarks on ARM64 with this code
commented on GCC mainline and I haven't observed any perf regression. So, maybe
worth a fix.

Thank you.